Mash and strain raspberries, reserving juice. Discard seeds. Add enough water to juice to measure 2 cups; pour into a large saucepan. Add grape juice, sugar and lemon zest strip. Bring to a boil; reduce heat. Simmer, uncovered, for 10 minutes.
Remove lemon zest strip. Add tapioca. Cook and stir for 10 minutes. Pour into bowls. Cover and chill for 4 hours or until set.
In a bowl, beat cream and confectioners' sugar until soft peaks form. Serve with pudding.